The condenser quasicentral modulus

Abstract

We introduced the quasicentral modulus to study normed ideal perturbations of operators. It is a limit of condenser quasicentral moduli in view of a recently noticed analogy with capacity in nonlinear potential theory. We prove here some basic properties of the condenser quasicentral modulus and compute a simple example. We also discuss some associated variational problems. Part of the results are in the more general setting of a semifinite von Neumann algebra.

26 pages. added sections 7 and 8 and made the necessary additions to the introduction and abstract. Minor corrections. Further addition to section 8.Further addition to section 3. Typos corrected